[Stan Weiss]

When talking about area under the curve. Should we be talking about using the lifter raise curve or the valve lift curve? Because the valve lift area sure looks different with 1.5:1 ratio rocker arms than with higher ratios.

Stan

[Tiger Paw]

Sure, your graph illustrates increased lift and the increased duration at .200. Changing cams without changing cams.

However big rocker ratios stress other components and require more frequent checks, maintenance and even can require heavier duty parts. Going from 1.5 to 1.6 isn't a big deal if you have the room, but going 1.7 and up can be.

[Steve C.]

Stated- "Should we be talking about using the lifter raise curve or the valve lift curve?"

They will be different. As the engine runs the cam will loose area under the curve.
Example for Comp XE hydraulic roller lobe 3315

First two, as measured on a 'cam Dr' :

Duration 'on the tappet' ( 0.0006" )
282 degrees duration

Duration measured 'at the valve' itself with a true 1.5 rocker ratio
288 degrees duration

Third, duration as measured on a Spintron machine under running conditions:
About 278 degrees (it will vary, example with lifter pre load, push rod flex and the lifter 'gives' just a little as you load it under running conditions, thus the 10 degrees less duration measured at the valve)

Lobe is rated 230 degrees at .050" tappet lift

Max lift at the tappet 0.3400" (lobe lift)
Max lift at the valve w/1.5 ratio 0.5100"
Max lift under running conditions about 0.5040"

Area thru the entire lift curve from the tappet (.0006) thru max lift is 55.22
At the valve it's 82.8 (w/1.5 ratio)
At the valve under running conditions 80.9 (w/1.5 ratio)

Similar situation happens on a solid cam when you factor in valve lash.


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[mkpontiac]

From Steve C quoting UD Harold that all of his designs have a hydraulic Intensity of 53.88 degrees at 0.004 tappet lift would this mean that the Voodo advertised duration of the 702 cam for instance would be 219+53.88=272.88 at 0.004" compared to the actual advertised duration of 262 presumably at 0.006"?

[pastry_chef]

Originally Posted by mkpontiac

From Steve C quoting UD Harold that all of his designs have a hydraulic Intensity of 53.88 degrees at 0.004 tappet lift would this mean that the Voodo advertised duration of the 702 cam for instance would be 219+53.88=272.88 at 0.004" compared to the actual advertised duration of 262 presumably at 0.006"?

Could be true. I noted the same posted by Harold Sept 15, 2009.
http://forums.maxperformanceinc.com/...4&postcount=58

Here is a quote about the advertised rating. Might explain why some newer cam cards differ from the adv catalogue values.

Originally Posted by UDHarold
First of all, Lunati/Holley kept the computer and the printouts, so I cannot go back and reference what the actual numbers were.
When the VooDoos were first designed, several Sales Managers and a different owner ago, Lunati decided that they would compete directly with the Xtreme Energy cams at seat duration. I believe the actual ramp height was around .0068"-.0070" high.
The .050s were .050", the .200s were .200", as expected.

[mkpontiac]

pastry_chef
It all seems to make sense. I am just trying to make a comparison between cams at 0.004 tappet lift for calculating dynamic compression.
Thanks,

[Steve C.]

A tid bit here for interest only.....

"The Lunati Voodoo cams are not old Ultradyne cams, although as designer of both there are certain similarities. Both are unsymmetrical, with aggressive opening sides and gentle seating ramps (to control seating noise). The specs on the Voodoo's are set by Lunati's former sales manager as far as lift and duration. The shape of the curve is the way I design, the names Ultradyne and Voodoo aren't interchangeable."
Harold Brookshire

Also another fwiw tid bit, Lunati does not have any of Harold's original UltraDyne lobe masters. Some of the cams Lunati sells with the 'same' specs as the old UltraDyne cams are not ground with actual UltraDyne masters. Lunati pirated the UltraDyne masters and made copies before Harold was fired by Lunati. All the original UltraDyne masters were sold to Bullet Racing Cams who also have the rights to the UltraDyne name.


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[Steve C.]

Dynamic Compression Ratio

http://members.uia.net/pkelley2/DynamicCR.html


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[pastry_chef]

Originally Posted by Steve C.

Also another fwiw tid bit, Lunati does not have any of Harold's original UltraDyne lobe masters. Some of the cams Lunati sells with the 'same' specs as the old UltraDyne cams are not ground with actual UltraDyne masters

From the horse's mouth

by UDHarold » Sat Dec 16, 2006 12:49 am
Bullet bought UltraDyne, and got everything that was there when they bought it. They let the CNC machine with the program for making those great roller lifters go back to the CNC company, they didn't want to pay that last $12,500 to pay off the Fadal.
However, before they bought UltraDyne, Lunati made copies of all the masters off the finish masters, the best UltraDyne had.
So Lunati and Bullet both have the UltraDyne masters; only Bullet has the right to call them UltraDynes.

https://www.speed-talk.com/forum/viewtopic.php?t=4793

[pastry_chef]

Vizard is one of the few experts who value DCR. A great article here.
https://www.hotrod.com/articles/0311em-power-squeeze/


I personally looked at it and played with the math back in the 90s.. but stopped shortly after.

Harold Brookshire

The intake valve closing point mainly tells where the intake valve closes. Get your favorite cam grinder to grind 2 cams with the identical profiles, but with TWO different LSAs, say 106 and 108, or 110 and 112. Install one cam in the engine, then dyno it. Install the other cam on the IDENTICAL intake centerline, so that opening and CLOSING points are the same for both cams. The cams will have different cranking compressions, different power curves. This is not to say one is better than the other, only different. What effects the REAL dynamic compression is HOW MUCH air and gas is in the cylinder when the intake valve closes, not at what degree ABDC the valve closes. The different exhaust opening points affect the amount of back pressure, ie, reversion, that is present when the intake valve opens BTDC. The amount of reversion affects the rate of cylinder filling on the intake stroke, and the amount of air and gas in the cylinder when the intake valve closes. This is what gives you the actual Dynamic Compression. The operative word is DYNAMIC. Other cam designers may differ in opinion. UDHarold

Mike Jones

There are two major errors with the thinking behind DCR.
1: That air flow into the engine, stops at BDC.
2: That compression doesn't start, until the intake valve closes.
Both are 100% incorrect.

There's nothing Dynamic about DCR, and it has no mathematical significance to what's going on in a running engine.
DCR is based on the misconception that you need the intake valve to be closed, to start compressing the mass in the cylinder, and that's far from the truth. As long as the pressure above the intake valve is higher then the pressure below the intake valve, the open valve will not bleed off any compression.

Chris Straub

I pay no attention to DCR. The acronym itself is a contradiction. Dynamic (Constantly Changing) Ratio
(difference between 2 set numbers). To me it is worthless.
Making power is all about making pressure. To control the pressure you must be able to manipulate
valve events. That's the key to my success over the years.

[Steve C.]

Correct, Lunati made copies of all the UltraDyne masters. The original masters went to Bullet racing.

Semantics


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[pastry_chef]

Originally Posted by Steve C.

Semantics

Depends if you are suggesting Harold's lobe blueprint would be degraded by using a master 'copy'. Even ordering the same lobes from the same company can result in more end variation (depending on the machine).

[Stan Weiss]

Another question would be how much use did a master have and how close was the last cam ground with that master to the first cam ground cam ground with that master?

Stan

[pastry_chef]

Originally Posted by Stan Weiss

Another question would be how much use did a master have and how close was the last cam ground with that master to the first cam ground cam ground with that master?

Stan

Agree.. and the relevance to Harold's

copies of all the masters off the finish masters, the best UltraDyne had.

[Stan Weiss]

Mike,
I have no idea about these masters and how much use they had. But whoever has Harold's original work can use that to create a band new master if needed.

Stan

[pastry_chef]

It would be interesting to know about UD blueprint remains, outside of masters.
Mike O'Neal created those masters when he worked at Ultradyne, he was the first hire Sept, 1981.
After Ultradyne closed Mike, Steve and eventually Harold went to work for Lunati.
Mike was still there in 2009. Not sure why they would copy a finish master if you have the raw blueprint. Before Bullet purchased UD remains.

[TCSGTO]

I’ve never ground a cam or worked in a shop that so I’m confused by some of the terms thrown around. “Master” seems to refer to an actual hard copy camshaft most of the time but then also as a CAD master drawing.
Once you have the CAD to write a CNC machining and CMM inspection programs what would need a physical “master” for? Just trying to learn the process here.

[Stan Weiss]

Originally Posted by pastry_chef

It would be interesting to know about UD blueprint remains, outside of masters.
Mike O'Neal created those masters when he worked at Ultradyne, he was the first hire Sept, 1981.
After Ultradyne closed Mike, Steve and eventually Harold went to work for Lunati.
Mike was still there in 2009. Not sure why they would copy a finish master if you have the raw blueprint. Before Bullet purchased UD remains.

Mike,
From what I understand it is quicker to copy a master than to create a new one. which means less $$$$$ spent.

Stan

[Stan Weiss]

Originally Posted by TCSGTO

I’ve never ground a cam or worked in a shop that so I’m confused by some of the terms thrown around. “Master” seems to refer to an actual hard copy camshaft most of the time but then also as a CAD master drawing.
Once you have the CAD to write a CNC machining and CMM inspection programs what would need a physical “master” for? Just trying to learn the process here.

From what I understand many cams are still ground the old fashion way on manual cam grounders and therefore the need for a lobe master.

Stan

[Steve C.]

"Depends if you are suggesting Harold's lobe blueprint would be degraded by using a master 'copy'."

Not my intention.

There are some interesting material out there related:

http://www.superchevy.com/how-to/eng...ing-technology

https://www.youtube.com/watch?v=g5T2eerPtkg


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